The present invention relates to an optometric apparatus suitable for correction of refraction and visual function analysis of an eye to be examined.
When a refractive error (ametropia) is present in an eye to be examined and is to be corrected, it is important to prescribe such a power that will not impart an uneasy sensation and fatigue to a subject in wearing the spectacles after accurately examining the refractive state of the eye to be examined and by taking into consideration the complaints of the subject and powers of the former spectacles. In addition, if a visual function error such as phoria is present in the eye to be examined, it is necessary to analyze that visual function correctly and correct the same.
When determining a prescription power, a perfectly corrected refractive power test is generally conducted on the basis of data on examination such as an objective examination using a so-called refractometer and the measurement of powers of the former spectacles using a lens meter. In the perfectly corrected refractive power test, a subjective-type refractive-power measuring device in which optical elements having various optical characteristics are selectively disposed in test windows is used, responses on appearances of a presented test target (chart) is obtained from the subject, and a power at which maximum visual acuity can be obtained is determined. After a perfect correction power is obtained in the perfectly corrected refractive power test, the power adjustment is made on the basis of this power and the like, and prescription values are derived.
However, the procedure for deriving appropriate prescription values after obtaining the perfect correction power and adjusting that power largely depends on the knowledge and experience of the examiner, and is not easy for an inexperienced person.
There have been problems in that, particularly in a case where a visual function error such as phoria is present in the eye to be examined, substantial time is generally required in deriving prescription values after making power adjustment, and that there are differences in the derived prescription values among individual examiners.